1. Introduction
The present invention relates generally to improved illumination apparatus and methods for control of light reflections from reflective surfaces. In one preferred aspect, the invention relates to illumination apparatus such as used on motor vehicles that can present a more aesthetically pleasing appearance and that can more effectively manage the reflection of incident light than previously known devices.
2. Background of The Invention
In the styling of vehicles, such as automobiles, it is often desirable to integrate the various kinds of lights that must appear thereon into the overall design of the vehicle. These lights such as illumination lights, e.g., headlights or back-up lights, or signal lights, e.g., tail lights, side lights, or turn signal indicators, traditionally have a bright, reflective appearance, and sometimes have a colored appearance, such as a red or yellow color, e.g., colors often used for signal lights. Even when the light is turned off and it is not operative for performing its illumination or signaling function, these bright and/or colored areas on an automobile, for example, call undue attention to themselves or produce a considerable, and often unpleasing, contrast with the color of the rest of the vehicle. From a aesthetic design point of view, such factors are often not desirable.
At present the only known practical ways either to suppress the undesired brightness or color of such vehicle lighting or to match the color of the lights to the body color of the vehicle are to retract the lights into the vehicle's body or to hide them behind a panel, or other suitable cover, when they are not in use, e.g., when headlights are not used during the day. Alternatively, a very dark lens may be used as the output lens of the light or the lens may be covered with a very dark gray filter, as is often done with tail lights, to provide a solid, dark appearance and contrast with the body color of the vehicle.
These techniques clearly have some disadvantages. In the case of the use of retracting lights or cover panels there are the mechanical complexities involved, as well as the added weight and cost of the various mechanisms used. In the case of the use of very dark lenses or filters, there is the problem of the diminution of the light output and the need to use a higher wattage lamp in order to regain a part of the illumination output that is lost.
Accordingly, it is highly desirable to devise effective and more economical techniques for providing a lighting device which will appear as an opaque surface when turned off, but which still functions efficiently as an illumination or signal device when turned on.
Further, such illumination or signal devices often contain one or more lenses or other reflective surfaces. For example, motor vehicle lights typically contain a rear reflector plate positioned behind the light source that assists the light transmission outwardly through a forward lens. The forward lens of a motor vehicle light can also reflect external incident light, e.g., sunlight, moonlight or starlight, or artificial light such as light from the lights of other motor vehicle or electric lights present in the environment, especially from the facets or lens-like elements at the rear surface of the lens which elements provide the desired light beam pattern.
Such reflections may be of serious concern or even be dangerous, for example in military vehicles where such reflections can reveal the position of a vehicle to an enemy. For instance, a motor vehicle illumination device such as a headlight, even though not in operation, can reflect sunlight, moonlight or starlight and expose an otherwise camouflaged vehicle's location. Also scanning devices that rely upon reflections of incident beams, such as laser beams, have been used to locate such vehicles.
Prior techniques for reducing such reflections have included covering of the motor vehicle lights during the daytime by a suitable non-reflective material or, in some cases, smearing the light with mud or dirt or other debris to at least partially reduce the reflective nature thereof. Such techniques are inconvenient and are often not effective or can easily be forgotten in hectic situations such as under battle conditions.
Another useful means for reducing light reflections from reflective surfaces has been disclosed in my U.S. Pat. No. 4929055, issued on May 29, 1990, which is incorporated herein by reference. Such technique, if used internally, while generally reducing most reflections from an external light source that are mostly due to the rear reflecting surface of a light device, does not reduce the remaining reflections from the front and rear surfaces of the forward lenses of the device. This is because the rear reflective surface of the lens is, in a motor vehicle, typically made up of many small, lens-like or prism-like elements which perform the light concentration, dispersion or beam forming function of the device. These small elements often reflect external incident light present in the environment back to a viewer. Such reflections both de-saturate the apparent color, if any, that such an internal structure may have been painted and also make the light device appear as a bright, easily discernible surface. It is desirable, to devise a technique for more effectively reducing these remaining reflections.